No abstract

All-nanoparticle thin-film coatings that exhibit antireflection, antifogging (superhydrophilicity), and self-cleaning properties have been prepared via layer-by-layer deposition of TiO(2) and SiO(2) nanoparticles. The porosity and chemical composition of the coatings were determined using a simple method that is based on ellipsometry and does not require any assumptions about the refractive indices of the constituent nanoparticles. The presence of nanopores in the TiO(2)/SiO(2) nanoparticle coatings results in superhydrophilicity as well as antireflection properties. The superhydrophilicity of contaminated coatings could also be readily recovered and retained after ultraviolet irradiation.

Using a combination of an aqueous layer-by-layer deposition technique, nanoparticle surface modification chemistry, and nanoreactor chemistry, we constructed thin film coatings with two distinct layered functional regions: a reservoir for the loading and release of bactericidal chemicals and a nanoparticle surface cap with immobilized bactericides. This results in dual-functional bactericidal coatings bearing both chemical-releasing bacteria-killing capacity and contact bacteria-killing capacity. These dual-functional coatings showed very high initial bacteria-killing efficiency due to the release of Ag ions and retained significant antibacterial activity after the depletion of embedded Ag because of the immobilized quaternary ammonium salts.

Antibacterial coatings based on hydrogen-bonded multilayers containing in situ synthesized Ag nanoparticles were created on planar surfaces and on magnetic colloidal particles. We report the antibacterial properties of these coatings, determined using a disk-diffusion (Kirby-Bauer) test, as a function of the film thickness and the concentration of Ag nanoparticles in the hydrogen-bonded multilayers. The zone of inhibition (ZoI) determined by the disk-diffusion test increases as the thickness of the multilayer film is increased. Results obtained for the values of the ZoI as a function of film thickness can be described adequately with a simple diffusion model (i.e., the square of the zone of inhibition (ZoI) depended linearly on the logarithm of the thickness of the silver-loaded films). This observation suggests that, in order to incrementally increase the ZoI, an exponentially increasing amount of Ag is required within the multilayers. In general, there was no statistically significant correlation between the zone of inhibition and the number of Ag loading and reduction cycles. The duration of sustained release of antibacterial Ag ions from these coatings, however, could be prolonged by increasing the total supply of zerovalent silver in the films via multiple loading and reduction cycles. These results indicate that the release of silver is controlled by an oxidation mechanism at the surface of the nanoparticles and that repeated loading and reduction of silver leads preferentially to growth of the existing silver nanoparticles in the film as opposed to nucleation of new Ag nanoparticles. We also show that magnetic microspheres coated with silver nanoparticle loaded hydrogen-bonded multilayer thin films can be used to deliver antibacterial agents to specific locations. The minimum inhibitory concentration (MIC) of nanocomposite coated microspheres was determined by the agar dilution technique: antibacterial magnetic microspheres with higher concentrations of Ag nanoparticles exhibited lower MIC values.

Nanoparticle colloidosomes, shown in the SEM image, are generated by using water‐in‐oil‐in‐water double emulsions as templates. Hydrophobic silica nanoparticles that are dispersed in the oil phase stabilize the double emulsions, and subsequently become the shell of the colloidosomes upon removal of the organic solvent as shown in the figure.